The present invention pertains to an improved small profile tool for tightening strap around an object or load and adhering the strap onto itself. More particularly, the present invention is directed to a pneumatic circuit and module for a strapping tool that is configured to tension a strap around a load, weld or melt-adhere the strap onto itself and sever the strap from a strap source (e.g., supply).
Strapping tools are well-known in the art. These tools come in a wide variety of types, from fully manual tools to automatic, table-top tools. Tools are generally designed for use with either metal strapping or plastic/polymeric strapping.
Strappers for applying plastic or polymeric strapping materials can be of the automatic table-top or hand-held devices and are either electrically or pneumatically driven. This is necessary in order to provide energy for tensioning the strapping material and adhering the strap onto itself. Typically, the adhering function is provided by melting or otherwise welding a section of the polymeric (plastic) strapping material onto itself. Such melting or welding operations are generally carried out using ultrasonic or vibrational-type weld assemblies. The movement or vibrational motion can be provided by electrical, electromechanical or fluid drive (hydraulic or pneumatic) systems.
In one exemplary tool, a pneumatic system is used to drive the motors to tension the strap (driving a tensioning wheel), and to move a vibrating element that is in contact with interfacial surfaces of overlapping plastic strap portions. The tool includes a pneumatic circuit to route the compressed gas (air) to the appropriate functional elements (clamps and motors) through valves and the like.
In such a tool, the various functional elements are large and as such can be cumbersome. In addition, many such tools use one or more large (and heavy) mechanical clutch(es) to hold or clamp the strap following tension.
Accordingly, there exists a need for a pneumatic strapping tool that uses separate pneumatic motors (one motor for tensioning or feeding strap and another for welding the strap material onto itself) in a small or low profile package. Desirably, such a tool incorporates a pneumatic circuit that allows eliminating the clutch (and thus the weight) otherwise necessary for clamping the strap during welding and roll-back to facilitate operation. Most desirably, for ergonomic considerations, the pneumatic module is of a two button design to facilitate operation and to prevent actuation of the tensioning cycle (motor) during the sealing cycle.